Method of and apparatus for cooling of rotational casting apparatus

ABSTRACT

The casting apparatus includes an oven and a cooling chamber and a cooling tank is provided at the bottom of the cooling chamber while spray nozzles are positioned in the cooling chamber for spraying water onto molds therein for cooling action. A pump means connects to the cooling tank and to the spray nozzles for forcing water therethrough, which pump means also connects to a water-circulating system connecting to the oven doors for circulating cooling water therethrough. Improved oven door seal means are present. The invention also relates to a method of circulation of mold-cooling water.

United States Patent Boyce [54] METHOD OF AND APPARATUS FOR COOLING OF ROTATIONAL CASTING APPARATUS [72] Inventor: Alden C. Boyce, Stow, Ohio [73] Assignee: Rota-Matic, Inc., Summit, Ohio [22] Filed: Apr. 9, 1970 [21] Appl. No.: 26,860

[52] US. Cl ..l65/48, 165/107 [51 I Int. Cl ..F25b 29/00 [58] Field of Search ..165/2, 48, 86, 107, 47

[56] References Cited UNITED STATES PATENTS 3,138,241 6/1964 Dahlman ..l65/86 CHAMBER Feb.8,1972

Primary ExaminerCharles Sukalo Attorney-Oldham & Oldham [5 7] ABSTRACT The casting apparatus includes an oven and a cooling chamber and a cooling tank is provided at the bottom of the cooling chamber while spray nozzles are positioned in the cooling chamber for spraying water onto molds therein for cooling action. A pump means connects to the cooling tank and to the spray nozzles for forcing water therethrough, which pump means also connects to a water-circulating system connecting to the oven doors for circulating cooling water therethrough. Improved oven door seal means are present. The invention also relates to a method of circulation of mold-cooling water.

5 Claims, 5 Drawing Figures PATENIED FEB 8 I972 SHEET 2 [IF 2 CONTROL 2o so\ PANEL H63 22 l go P 90 90 I 64 I PR3 \?'E. 90 M22 \EUJ INVENTOR. ALDEN C. BOYCE BY WWW ATTORNEYS.

METHOD OF AND APPARATUS FOR COOLING F ROTATIONAL CASTING APPARATUS The present invention relates generally to rotational casting apparatus and methods, and especially to means for cooling the molds and to means to provide an improved oven door seal.

BACKGROUND OF THE INVENTION Heretofore there have been many different types of rotational casting apparatus provided for forming articles from plastic materials, such as liquid plastisols of vinyl resins and the like, or for forming articles from solid plastic resins, such as polyethylene powders and the like. These machines normally require ovens heated to relatively high temperatures, such as 500' to 700 for setting up or fusing the plastic materials being processed, and the apparatus normally includes a plurality of mold support spindles carried by a driven center support for progressively moving the molds into the oven and cooling chamber. These molds are heated to relatively high temperatures, such as about 500 F. to as much as about 900 F. for article formation and setting action in the ovens, and then the molds and the articles formed therein must be cooled to some type of a reasonable temperature for mold-handling, opening and mold-refilling actions. Inasmuch as it is always desired to obtain as much production as is possible from a given machine, naturally it is quite important that the molds be retained as warm as possible when cooled for opening, and to provide a relatively fast, complete cycle in the apparatus between introducing new article-forming material into the mold cavities, the heating thereof, and the cooling of the molds to complete the article-forming cycle.

Another problem in apparatus of this type is the water used therein, and it is always very important that the oven has end doors thereon to seal the same tightly under all operating conditions. However, it is difficult to preserve good seals for these oven doors because of the quite high temperatures to which one side of the door is subjected when it is in use.

The general object of the present invention is to provide a novel and improved method of an apparatus for sealing the oven doors and for cooling the molds efficiently in the cooling chamber in plastic-casting apparatus.

Another object of the invention is to provide an improved apparatus by which the cooling water in the apparatus is preheated prior to being sprayed onto mold for cooling action so that an excessive temperature gradient does not exist and the sprayed water does not just bounce off of the hot mold without providing any effective cooling action thereon.

A further object of the invention is to seal the oven doors effectively in closed positions.

Another object of the invention is to provide suitable means and controls in apparatus of the type described wherein cooling action cannot be obtained in the cooling chamber until the water present therein has reached a desired operating temperature and wherein the cooling water is preheated by being circulated through the doors on the oven and with each door having a cooling fluid continually circulating therethrough when the apparatus is in use.

The foregoing and other objects and advantages of the in vention will be made more apparent as the specification proceeds.

For a better understanding of the present invention, attention is directed to the accompanying drawings, wherein:

FIG. I is a plan view, diagrammatic, of a portion of a rotational casting machine having an oven and cooling chamber therein;

FIG. 2 is a fragmentary elevation, partly broken away and shown in section, of the cooling chamber of FIG. 1;

FIG. 3 is a diagrammatic plan view of the cooling chamber of FIG. I with a portion of the control instruments and oven section being operatively associated therewith;

FIG. 4 is a somewhat diagrammatic elevation of a door of the oven of FIG. 1;

FIG. 5 is a fragmentary elevation, taken on line 5-5 of FIG. 4 of the oven door and its mounting means; and

FIG. 6 is an elevation like FIG. 5 but partly shown in vertical section and taken on line 66.

When referring to corresponding members shown in the drawing and referred to in the specification, corresponding numerals are used to facilitate comparison therebetween.

INVENTIVE SUBJECT MATTER In the present invention, a novel method of preheating and recirculating cooling water has been provided, which method includes the circulation of cooling water through the oven closure doors and return to the cooling chamber for use therein in spraying the water onto molds being processed in the cool ing chamber. In addition, apparatus is provided including a cooling tank having an open top positioned at the bottom of the cooling chamber, spray nozzles positioned adjacent the top and bottom of the cooling chamber, pump means operably connecting to the cooling tank and the spray nozzles for forcing water through the spray nozzles, and wherein water-circulating means are provided and connected to the doors of the oven for waterflow therethrough. Other means aid in retaining the oven doors tightly closed.

FIG. 1 of the drawings shows a rotational casting apparatus 10 embodying the principles of the invention and wherein such apparatus includes a suitable center support 12 which has one or more support spindles or arms 14 secured thereto and extending therefrom. These arms 14 are adapted to have molds secured to ends 16 on such arms in the usual manner. The center support 12 is provided with any known drive means, not shown, and the entire apparatus is shown diagrammatically in the accompanying drawings, whereby the center support is rotated in the direction shown by the arrow 18. This is adapted to move the arms 14 into an oven 20 and then into a cooling chamber 22 with such oven and cooling chamber 22 being positioned in circumferentially spaced relationship to the center support 12 at the same distance therefrom whereby any mold or molds carried by the arm or arms 14 through an operative cycle can be opened when such arm is moved by the center support 12 to an open area between the cooling chamber and oven. At such open station, or stations, the molds can be opened articles stripped therefrom, new article forming material introduced, the molds closed, and then the apparatus would be ready to index or move such mold support arm 14 to the next station, i.e., the oven 20 for rotation therein for a controlled length of time after which the center support 12 would index or move another circumferential distance and the arm 14 would be positioned in the cooling chamber 2 2 for mold and article cooling action for the predetermined cycle time.

FIG. I of the drawings clearly shows that the ends of the cooling chamber 22 and of the oven 20 normally terminate on radially extending lines in relation to the center support 12 and suitable individual doors 30 and 32 are provided at each end of the oven 20. These doors are positioned for sliding movement, usually horizontal, to and from closing position engaging the remaining portions of the oven 20 for sealing the same for circulation of suitable hot air, burning gases, etc., therein. FIG. 4 brings out that the doors 30 and 32 have a hollow edge section, frame or jacket 33 extending therearound. A water inlet means 34 is provided at the bottom of the door and a water outlet means 36 is provided at the top of the door. Hence a water-cooling flow path is provided around the margins of the door as the cooling water will flow through the edge section or jacket 33 as indicated in FIG. 4. Since this oven in operation will be at high temperatures, such as 500 F. or more, and water is supplied thereto at room temperature, the water normally increases in temperature to about to as circulated through the door, as hereinafter described in more detail, and this maintains the edge section 33 in a cooled condition. War-page of the door thus can be prevented.

FIG. 2 of the drawings best shown that a relatively shallow large area, open top cooling tank 50 is formed or provided at the bottom of the cooling chamber 22 and normally occupies the entire bottom area thereof. Any suitable water supply means (not shown) operatively connects to the cooling tank to introduce more cooling water thereto, as desired. A pump 52 is positioned immediately adjacent or in the cooling tank 50 and it has a suitable inlet connecting to the tank whereby when this pump 52 is driven as by a conventional motor 53, cooling water is forced to flow therefrom through a vertically extending outlet pipe 54 normally extending the height of the cooling chamber. This outlet pipe 54 connects to a T-coupling or the like 56 from which a tube or pipe 58 extends and with the pipe 58 individually connecting to the water inlets 34 provided in each of the doors 30 and 32. Water returns from the doors 30 and 32 through a pair of pipes 60 and 62 that lead back to the top of the cooling chamber as shown in FIG. 3. There individual flow regulator valves, indicated at 64 and 66, are provided in each of the return pipes and conventional controls or leads 68 and 70 extends, respectively, from each of these controls or valves 64 and 66, to a control panel 80 with suitable instrumentation to indicate whether or not water is returning from both of the doors 30 and 32 at a predetermined rate. If water is not returning from both doors, then a suitable warning signal may be given or the apparatus could be shut off. The preheated water passing through these controls 64 and 66 is discharged back into the cooling tank 50.

Inasmuch as some water is continually lost in the system, additional water may be supplied thereto through a supply line 72 that connects to a city water supply or the like. A manually operated shutoff valve 74 is provided in this line for additional water supply as desired and a bypass line 76 is provided around the valve 74. In this bypass line 76, an electrically controlled, or solenoid-actuated valve 78 is provided and this valve may be controlled by a suitable temperature control means 81, such as a thermostat or equivalent member that may be electrically coupled to the control panel 80 and also to a thermostat 79 positioned in the water in the cooling tank to sense the temperature thereof. Hence, water can be automatically fed into the system at any time, for example, when the temperature thereof is above a desired operating temperature, such as above 130 F. or if the use of hotter water is desired, heaters may be provided in the cooling tank 50 and the system be set to operate with hot water such as at about 200 F.

In order to prevent excess water from being fed to the cooling tank 50, it usually is desirable to provide some type of a float-controlled switch means that operatively connects to the control panel 80 and/or to the solenoid valve 78 to permit the introduction of additional water only when insufiicient water is present therein.

It has been found in the practice of the invention that use of water at room temperature or lower does not work very well for mold-cooling action. Water at about 50 to 75 F. does not seem to cool a hot mold at a temperature of 350 F. or higher rapidly when sprayed thereon because the water particles just bounce off of such hot mold and do not tend to run therealong or stay thereon, and such water tends to be turned into steam more readily than water at a higher temperature. However, with water of temperatures of at least about 120 to about 150 F., the water seems to run along the mold surface better and not bounce off the same so that a more efficient, improved, cooling action is obtained. Usually the cooling chamber has some type of doors at each end thereof to aid in retaining the water sprayed around in the cooling tank within the cooling chamber for dropping down into the cooling tank provided.

The pump 52 is of any suitable capacity and will, for example, pump or have an outlet of water of from about 85 to 100 gallons per minute. The flow control valves 64 and 66 are set up to measure waterflow of approximately 2 gallons per minute. Hence, when these valve do not have such waterflow therethrough, they will send proper signals to the control panel 80 for alarm or apparatus shutdown purposes, as desired. By reuse of the water used for cooling the oven doors, and by reuse ofthe mold-cooling water so as to utilize the heat flow to such water to obtain improved cooling action in the cooling chamber, and improved, efficient system is obtained and the objects of the invention have been achieved.

Other controls may be provided. For example, by using a programmed timer control action, a solenoid valve 82 in line 54 may be activated at preset time to allow water to pass through the cooling spray nozzles. Such valve 82 is controlled by means on the control panel 80. The valve 82 preferably is of the pneumatic diaphragm type. This spray nozzle means in the apparatus may comprise a plurality of nozzles positioned adjacent the upper portion of the cooling chamber 22 and a plurality of nozzles 92 of any suitable type positioned adjacent the bottom of the cooling chamber. Pipes 94 connect these nozzles 90 and 92 to the water outlet supply line 54 whereby a uniform spraying action and cooling can be obtained on a mold positioned within the cooling chamber. Usually at that time, the mold is still being rotated on both axes, so that the cooling water will be applied in a substantially uniform manner over all surfaces of the mold while the spindle or arm on which the mold is positioned is not moving circumferentially but with the apparatus being indexed to stop rotation of the center support 12 for the mold-cooling action.

The cooling chamber 22 normally has a large fan or fans 98 provided therein for drawing large volumes of cooling air into a cooling chamber, and which air passes over the cooling tank 50 and then usually is exhausted from the cooling chamber by an exhaust fan 100, of conventional construction, provided at the top of the cooling chamber. Hence, large volumes of air will be drawn into and through the cooling chamber to provide an air-cooling action when desired, or a combined air-andwater action when suitable.

If desired, fog-type spray nozzles may be used that direct their spray into the stream of cooling air provided by the fan or fans 98. Then no nozzles need to be placed specifically at the top or bottom of the oven but the nozzles would be directed to spray into the airblast at angles from adjacent the fans.

FIGS. 5 and 6 show certain added details on means for insuring that the oven doors stay in tight engagement with the oven frame for oven-sealing action. Thus, in FIG. 5, an oven door 32 is shown that is positioned for horizontal sliding movement to move to and from closure relationship with openings provided in the oven 20 at opposite ends thereof to aid in retaining heat provided within the oven therein. Any suitable seal means can be provided in association with a sidewall of the oven through which the arm 14 would extend, when the turret 12 is moved, for sealing or substantially sealing the same. Thus, a door 32 is shown positioned or guided in any suitable manner, such as on a plurality of rollers carried by a frame member 112 secured to the floor or support immediately adjacent the oven frame 114 in which the oven door opening is formed. In the structure shown in FIG. 5, the oven frame has an extension or bracket 116 that extends laterally from the side of the door opening remote from that direction in which the door 32 moves for opening action whereby the door will not actually move past the bracket 116 when moved to or from open or closed position. This bracket 116 mounts a suitable member, such as a pneumatic cylinder 118 thereon, which has an operative piston rod 120 extending therefrom and carrying a locking disc 122 at its end. The door has a bracket or extension plate 124 secured thereto and extending therefrom in the general plane of the door and the plate has a slot thereon for receiving the piston rod 120 when the door is moved to its fully closed position, as shown in FIG. 5. Then, by actuation of the pneumatic cylinder 118, the locking disc 122 can be moved forcibly towards the oven frame and clamp in engagement with the plate 124 to force the plate and the associated edge or comer portion of the door 32 into tight closed or sealing relationship with the oven frame 114 to aid in obtaining good effective sealing positioning of the door when the oven is in service.

At the opposite end of the door 32, a further pneumatic or hydraulic cylinder 126 is positioned, as by a vertically extending support 128. This cylinder 126 has a piston rod 130 extending therefrom and a pressure plate or plunger 132 is secured to the end of the piston rod 130. In this particular construction, the edge of the door 32 remote from the door frame opening has extension brackets 134 secured thereto and extending laterally therefrom. Thus, in closed position, the bracket 134 and plunger 132 are in axial alignment with each other whereby when the cylinder 126 is energized, the plunger 132 can be forced into engagement with the bracket 134 and force it toward the oven frame for effective door closure or sealing action.

Preferably one of the cylinders 118 is provided adjacent each of the top and bottom comers of one vertical margin of the oven door and a pair of the cylinders 126 are positioned correspondingly adjacent top and bottom margins of the other vertical margin of the door whereby the door is held in closed position by four locking means, one adjacent each of the corners of the door. The door may be slidably positioned by conventional hanger or guide means, but is free for slight movement toward and away from the oven when moved to and from oven-closing positions.

The apparatus of the invention is shown somewhat diagrammatically and electric leads, pneumatic or hydraulic connection lines and controls are omitted in some instances for clarity. The action of the cylinders 118 and 126 can, for example, be controlled from the control panel 80, if desired, to be actuated in proper timed relationship to the operative cycle of the machine. It will be realized that the machine moves through several indexes or stations at which time the turret 12 would not rotate but when molds carried on the support arms 14 can be rotated on plural axes in accordance with conventional practice.

From the foregoing, it is believed that the objects of the invention have been achieved.

While in accordance with the Patent Statutes, only one best known embodiment of the invention has been illustrated and described in detail, it is to be understood that the invention is not limited thereto or thereby, but that the inventive scope is defined in the appended claims.

What is claimed is:

l. [n a rotational casting apparatus for plastic materials including an oven and a cooling chamber arranged circumferentially of a rotatable center support having a mold support arm extending therefrom to position molds in said oven or said cooling chamber as said center support rotates, said oven having doors operably positioned at each end thereof, the improvement of spray nozzles positioned in said cooling chamber, means for collecting water sprayed by the nozzles, pump means operably connected to said means for collecting water and to said spray nozzles for forcing water through said spray nozzles to cool a mold positioned in said cooling chamber, said doors each having a waterflow circulation path formed therein, means connecting said pump means to said doors to circulate cooling water therein, and means for returning water from said doors to said means for collecting water. 2. An apparatus as in claim I, the improvement of individual waterflow return means connecting the individual ones of said doors to said means for collecting, and flow-measuring means provided in said flow return means for a control or warning action if a desired waterflow rate does not exist. 3. An apparatus as in claim 1, the improvement of said connecting means comprising dual water supply means connecting said pumped water for flow individually to each of said doors to flow around the periphery thereof, and second control means to indicate if water is not being returned from each of said dual water supply means. 4. An apparatus as in claim 1, the improvement of a plurality of clamp means operatively positioned adjacent the comers of each of said doors to force said doors tightly against said oven.

5. An apparatus as in claim I, the improvement of said doors being slidably posltloned relative to the oven frame and openings therein, and clamp means to engage said doors and force them tightly against said oven frame. 

1. In a rotational casting apparatus for plastic materials including an oven and a cooling chamber arranged circumferentially of a rotatable center support having a mold support arm extending therefrom to position molds in said oven or said cooling chamber as said center support rotates, said oven having doors operably positioned at each end thereof, the improvement of spray nozzles positioned in said cooling chamber, means for collecting water sprayed by the nozzles, pump means operably connected to said means for collecting water and to said spray nozzles for forcing water through said spray nozzles to cool a mold positioned in said cooling chamber, said doors each having a waterflow circulation path formed therein, means connecting said pump means to said doors to circulate cooling water therein, and means for returning water from said doors to said means for collecting water.
 2. An apparatus as in claim 1, the improvement of individual waterflow return means connecting the individual ones of said doors to said means for collecting, and flow-measuring means provided in said flow return means for a control or warning action if a desired waterflow rate does not exist.
 3. An apparatus as in claim 1, the improvement of said connecting means comprising dual water supply means connecting said pumped water for flow individually to each of said doors to flow around the periphery thereof, and second control means to indicate if water is not being returned from each of said dual water supply means.
 4. An apparatus as in claim 1, the improvement of a plurality of clamp means operatively positioned adjacent the corners of each of said doors to force said doors tightly against said oven.
 5. An apparatus as in claim 1, the improvement of said doors being slidably positioned relative to the oven frame and openings therein, and clamp means to engage said doors and force them tightly against said oven frame. 